Defrosting method of air conditioner

ABSTRACT

A defrosting method of an air conditioner is disclosed. The air conditioner has an indoor unit having an indoor heat-exchanger, an indoor blower fan, an auxiliary heater, an outdoor unit having an outdoor heat-exchanger, a compressor, an expansion device, and an outdoor blower fan, and a four-way valve to selectively switch a circulation direction of a refrigerant between the indoor unit and the outdoor unit such that the air conditioner is operated in a heating cycle when the four-way valve is turned off and the air conditioner is operated in a refrigerating cycle when the four-way valve is turned on. The defrosting method is selectively determined according to the number of the heating cycles of the air conditioner.

This application claims the benefit of Korean Patent Application No. 10-2005-0127973, filed on Dec. 22, 2005, which is hereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a defrosting method of an air conditioner, and more particularly, to a defrosting method of an air conditioner of effectively removing frost generated in pipes of an outdoor heat-exchanger by changing defrosting operation in a heating cycle.

2. Discussion of the Related Art

Generally, an air conditioner has a refrigerating cycle in which refrigerant circulates in the order of compression, condensing, expansion, and evaporation to transfer heat. Due to this refrigerating cycle, the air conditioner works in a refrigerating cycle in which indoor heat is discharged to the outdoor in summer season and serves as a heat pump in which the refrigerant circulates in a direction opposite to the direction in the refrigerating cycle to supply heat to the indoor in the heating cycle in the winter season.

In other words, when the air conditioner is operated in the heating cycle during the winter season, the refrigerant absorbs heat from a heat-exchanger of the outdoor unit to be evaporated and is condensed in a heat-exchanger of an indoor unit to discharge the heat. While the air conditioner operates in the heating cycle, since the outdoor unit absorbs heat, surface temperature of the outdoor unit is remarkably decreased. Due to the lowered surface temperature, on the surface of the heat-exchanger of the outdoor unit, frost is generated so that the efficiency of the heat-exchanger of the outdoor unit is deteriorated.

As a method of removing the frost generated on the surface of the heat-exchanger of the outdoor unit, there is a defrosting method of operating the air conditioner in the refrigerating cycle by circulating the refrigerant reversely during the heating cycle. In other words, if changing the operating cycle of the air conditioner from the heating cycle to the refrigerating cycle, the refrigerant in the heat-exchanger of the outdoor unit is condensed to discharge heat and the discharged heat removes the frost generated on the surface of the heat-exchanger of the outdoor unit.

FIG. 6 is a flowchart illustrating a conventional defrosting method of an air conditioner. As shown in FIG. 6, the conventional defrosting method starts a heating operation of the air conditioner (S1), and continues the heating operation for a predetermined time period (S2).

Continuously, a controller compares temperature of pipes of the outdoor heat-exchanger with a predetermined temperature (S3). At that time, when the temperature of the pipes of the outdoor heat-exchanger is equal to or less than the predetermined temperature, it is determined that frost is generated on the surface of the pipes of the outdoor heat-exchanger and the heating cycle is changed to the refrigerating cycle such that the defrosting operation is performed (S4).

When the defrosting operation is carried out, the outdoor heat-exchanger serving as an evaporator during the heating cycle serves as a condenser to emit heat, and due to the emitted heat, the frost covering the surface of the pipe of the outdoor heat-exchanger is started to be melted.

Continuously, the controller checks a defrosting operation finishing condition such as whether a time for the defrosting operation reaches a predetermined time from when the defrosting operation is started, or temperature of the outdoor heat-exchanger reaches the predetermined temperature (S5). For these reasons, if determining that the defrosting operation finishing condition is satisfied, the controller switches the cycle of the air conditioner from the refrigerating cycle to the heating cycle again to finish the defrosting operation (S6).

However, the conventional air conditioner carries out the defrosting operation condition when the temperature of the outdoor heat-exchanger is equal to or less than the predetermined temperature. Thus, when the temperature of the outdoor heat-exchanger is equal to or less than the predetermined temperature, the defrosting operation is frequently carried out regardless of the number of operation of the air conditioner in the heating cycle so that the heating efficiency of the air conditioner is deteriorated.

SUMMARY OF THE INVENTION

Accordingly, present invention is directed to an improved defrosting method of an air conditioner that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a defrosting method of an air conditioner of effectively removing frost generated on pipes of an outdoor heat-exchanger by changing defrosting operation according to a heating cycle.

An object of the present invention is to provide a defrosting method of an air conditioner including: an indoor unit including an indoor heat-exchanger, an indoor blower fan, an auxiliary heater; an outdoor unit including an outdoor heat-exchanger, a compressor, an expansion device, and an outdoor blower fan; and a four-way valve to selectively switch a circulation direction of a refrigerant between the indoor unit and the outdoor unit such that the air conditioner is operated in a heating cycle when the four-way valve is turned off and the air conditioner is operated in a refrigerating cycle when the four-way valve is turned on, the defrosting method being selectively determined according to the number of the heating cycles of the air conditioner.

Preferably, the defrosting method of an air conditioner includes: checking the number of the heating cycles of the air conditioner; determining whether a defrosting operation is to be started or not according to a defrosting operation starting condition based on the number of the heating cycles; firstly operating the air conditioner in the refrigerating cycle for a minimal defrosting time when the defrosting operation starting condition is satisfied in the determining; and re-determining whether the defrosting operation is finished or not according to a defrosting operation finishing condition based on the number of the heating cycles.

Here, in the checking, when the number of the heating cycles is equal to or less than 2, the defrosting operation starting condition comprises a case when the compressor is operated over a first accumulated driving time and pipe temperature of the outdoor heat-exchanger is equal to or less than a first freezing temperature.

Meanwhile, the defrosting method of an air conditioner further includes switching the operation cycle of the air conditioner to the refrigerating cycle when the defrosting operation starting condition is satisfied.

Here, in the switching the operation cycle to the refrigerating cycle, the compressor and the outdoor blower fan are switched to be turned off, the four-way valve is switched from a turning-off state to a turning-on state for a predetermined time period, and the auxiliary heater and the indoor blower fan are turned on when an indoor temperature is equal to or less than a predetermined temperature.

Meanwhile, in the firstly operating, the compressor and the four-way valve are turned on, and the auxiliary heater, the indoor blower fan, and the outdoor blower fan are turned off.

Here, the defrosting operation finishing condition may be a case when the pipe temperature of the outdoor heat-exchanger is equal to or greater than a first melting point.

Meanwhile, the defrosting method of an air conditioner further includes carrying out a heating operation after the firstly operating when the defrosting operation finishing condition is satisfied.

On the other hand, the defrosting method of an air conditioner further includes secondly operating the air conditioner in the refrigerating cycle until the defrosting operation finishing condition is satisfied when the defrosting operation finishing condition is not satisfied; and switching the operation cycle of the air conditioner to the heating operation.

Here, the secondly operating is not carried out without exceeding a first additional driving time, and the defrosting method further includes switching the operation cycle of the air conditioner to the heating operation regardless of the defrosting operation finishing condition when the defrosting operation finishing condition is not satisfied during the first additional driving time.

Meanwhile, in the secondly operating, the compressor, the four-way valve, and the outdoor blower fan are tuned on, and the auxiliary heater and the indoor blower fan are turned off.

Meanwhile, in the switching the operation cycle to the heating operation, the compressor and the outdoor blower fan are turned off, the four-way valve is switched from the turning-on state to the turning-off state for a predetermined time period, and the auxiliary heater and the indoor blower fan are turned on when the indoor temperature is equal to or less than the predetermined temperature.

In the checking, the defrosting operation starting condition, when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5, may be a case when the compressor is operated over for a second accumulated driving time and the pipe temperature of the outdoor heat-exchanger is equal to or less than a second freezing temperature.

Here, the defrosting method of an air conditioner may further include switching the operation cycle of the air conditioner to the refrigerating cycle when the defrosting operation starting condition is satisfied.

On the other hand, the defrosting method may further include switching the operation cycle of the air conditioner to the defrosting operation after performing the heating operation for an additional heating time when the pipe temperature of the outdoor heat-exchanger is under the second freezing temperature by measuring the pipe temperature of the outdoor heat-exchanger at a predetermined time interval when the pipe temperature of the outdoor heat-exchanger is equal to or greater than the second freezing temperature after the compressor is operated over for the second accumulated driving time at the defrosting operation starting condition.

Here, the defrosting operation finishing condition may be a case when the pipe temperature of the outdoor heat-exchanger is equal to or greater than a second melting point.

Meanwhile, the defrosting method of an air conditioner further includes switching the operation cycle of the air conditioner from the firstly operating to the heating operation when the defrosting operation finishing condition is satisfied.

Moreover, the defrosting method of an air conditioner further includes: secondly operating the air conditioner in the refrigerating cycle until the defrosting operation finishing condition is satisfied when the defrosting operation finishing condition is not satisfied; and switching the operation cycle of the air conditioner to the heating operation.

Here, the secondly operating is not carried out without exceeding a second additional driving time, and the defrosting method further includes switching the operation cycle of the air conditioner to the heating operation regardless of the defrosting operation finishing condition when the defrosting operation finishing condition is not satisfied during the second additional driving time.

In the checking, when the number of the heating cycles is equal to or greater than 6, the defrosting operation starting condition comprises a case when the compressor is operated over for a third accumulated driving time and pipe temperature of the outdoor heat-exchanger is equal to or less than a third freezing temperature.

Here, in the firstly operating, the compressor is turned off, the four-way valve is switched from a turning-off state to a turning-on state for a predetermined time period, the indoor blower fan and the outdoor blower fan are turned on, and the auxiliary heater is turned on when an indoor temperature is equal to or less than a predetermined temperature.

Meanwhile, the defrosting operation finishing condition may be a case when a pipe temperature of the outdoor heat-exchanger is equal to or greater than a third melting point.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

FIG. 1 is a schematic view illustrating a configuration of an air conditioner according to the present invention;

FIG. 2 is a block diagram illustrating the configuration of the air conditioner according to the present invention;

FIG. 3 is a flowchart illustrating a basic process of a defrosting method of an air conditioner according to the present invention;

FIG. 4 is a flowchart illustrating a process carried out when the number of performed heating cycles of the air conditioner in FIG. 3 is equal to or less than a predetermined number;

FIG. 5 is a graph illustrating a time point where the defrosting operation is started and a time point where the defrosting operation is finished according to pipe temperature of an outdoor heat-exchanger; and

FIG. 6 is a flowchart illustrating a conventional defrosting method of an air conditioner.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of a defrosting method of an air conditioner, examples of which are illustrated in FIGS. 1 to 5. In the description of the embodiments of the present invention, like references and like names of the components of the conventional ceiling type air conditioner described above with reference FIG. 2 are assigned to like components and their additional descriptions will be omitted.

FIG. 1 is a schematic view illustrating a configuration of an air conditioner according to the present invention, and FIG. 2 is a block diagram illustrating the configuration of the air conditioner according to the present invention.

Referring to FIGS. 1 and 2, the air conditioner according to an embodiment of the present invention includes an indoor unit 200 and an outdoor unit 400. The indoor unit 200 is installed in an air conditioning space, namely, in an indoor space 100.

An indoor inlet port 210 is positioned at the front side of the indoor unit 200, and an auxiliary heater 220, an indoor heat-exchanger 230, and an indoor blower fan 240 are provided at the rear side of the indoor inlet port 210. Air in the indoor space 100 is suctioned into the indoor unit 200 of the air conditioner through the indoor inlet port 210. The suctioned indoor air undergoes heat-exchange while passing through the indoor heat-exchanger 230 to adjust temperature of the suctioned indoor air and is discharged to the indoor space 100 through an indoor outlet port (not shown).

In this case, the indoor blower fan 240 serves to generate an air passage through which the indoor air is suctioned into the indoor unit 200 and is discharged out. The auxiliary heater 220 performs a defrosting operation during the heating operation to prevent temperature of the indoor space 100 from decreasing when the indoor heat-exchanger 230 servers as an evaporator.

Meanwhile, the indoor unit 200 further includes a power supply 201 to supply electric power to the air conditioner, an indoor temperature detector 202 to measure temperature of the indoor space 100, an indoor pipe temperature detector 203 to measure temperature of indoor pipes, an indoor blower fan driving unit 211 to drive the indoor blower fan 240, an auxiliary heater driving unit 212 to drive the auxiliary heater 220, and a controller 300 to control overall operation of the air conditioner.

The outdoor unit 400 is installed in a space outside of an air conditioning space, namely, an outside space to be connected to the indoor unit 200 through a pipe 250 through which a refrigerant flows. The outdoor unit 400 includes a four-way valve 410 to adjust a flowing direction of the refrigerant, a compressor 420 to compress the refrigerant into a high-temperature-and-high-pressure refrigerant, an outdoor heat-exchanger 430 to condense the refrigerant at a refrigerating cycle and to evaporate the refrigerant at a heating cycle, an outdoor blower fan 440 to generate an air passage through which indoor air is suctioned into the outdoor unit 400 and discharged out, and an expansion device 450 to expand the refrigerant into a low-temperature-and-low-pressure refrigerant.

On the other hand, the outdoor unit 400 further includes several devices to check an operating condition of the air conditioner and peripheral circumstance of the air conditioner in order to effectively control the air conditioner, typically, a detecting unit including an outdoor temperature detector 204 to measure outdoor temperature, an outdoor pipe temperature detector 205 to measure temperature of outdoor pipes, and an outdoor humidity detector 206 to measure outdoor humidity, and a driving unit including a compressor driving unit 213, an outdoor blower fan driving unit 214, and a four-way valve driving unit 215.

When a heating operation of the air conditioner according to the embodiment of the present invention is started, the controller 300 transmits a control signal to operate the respective driving units to the respective driving units. By doing so, the indoor blower fan 240 rotates, the compressor 420 compresses the refrigerant into the high-temperature-and-high-pressure refrigerant and discharges the compressed refrigerant. The high-temperature-and-high-pressure refrigerant discharged from the compressor 420 enters the indoor heat-exchanger 230 to perform the heat exchange with air suctioned into the indoor unit 200 by the indoor blower fan 240 so that temperature of the refrigerant is decreased. Temperature of the suctioned indoor air with relatively low temperature is increased by the heat exchange.

The refrigerant having undergone the heat exchange while passing through the indoor heat-exchanger 230 flows through the expansion device 450 and the outdoor heat-exchanger 430 sequentially and enters the compressor 420. After that, the refrigerant continues to sequentially circulate through the compressor 420, the indoor heat-exchanger 230, the expansion device 450, and the outdoor heat-exchanger 430 repeatedly to increase the indoor temperature to a desired indoor temperature.

On the other hand, during the repetition of the heating cycle, the detecting unit periodically checks a status of the air conditioner and the peripheral circumstance of the air conditioner, the controller 300 determines a present status of the air conditioner based on values detected by the detecting unit and adjusts the operating state of the driving units such that the air conditioner is effectively operated.

When a predetermined time period has been elapsed after the heating operation, frost is generated on the surfaces of the pipes of the outdoor heat-exchanger 430. The frost generated as described above is increased as the outdoor temperature is low and the time of performing the heating is increased. Since the frost generated on the surfaces of the pipes of the outdoor heat-exchanger 430 serves as a significant factor to deteriorate the heating efficiency of the air conditioner, the controller 300 performs a defrosting operation to remove the frost.

In a storing unit 310 of the air conditioner, a data table (namely, defrosting operation starting condition) for the defrosting operation is stored. The controller 300 periodically checks whether values measured by the detecting unit and a timer 320 are the same as values in the data table. If the measured values are identical to the values in the data table, the controller 300 directly controls the driving unit to perform the defrosting operation. The data and the defrosting operation will be described in detail later.

When the defrosting operation is performed, the outdoor heat-exchanger serving as an evaporator at the heating cycle serves as a condenser to emit heat, and due to the emitted heat, the frost covering the surface of the outdoor heat-exchanger begins to melt.

Hereinafter, the above-described defrosting operation starting condition and the defrosting operation will be described in detail with reference to the accompanying drawings.

FIG. 3 is a flowchart illustrating a basic process of a defrosting method of an air conditioner according to the present invention, and FIG. 4 is a flowchart illustrating a process carried out when the number of the performed heating cycles of the air conditioner in FIG. 3 is equal to or less than a predetermined number.

Referring to FIG. 3, the basic process of the defrosting method of an air conditioner according to the embodiment of the present invention includes a heating cycle checking step (S100) of checking the number of performed heating operation of the air conditioner, a determination step (S120) of determining whether the defrosting operation is started according to the defrosting operation starting condition based on the number of the performed heating cycles, a first defrosting operating step (S140) of operating the air conditioner in the refrigerating cycle for a minimal defrosting time t_(m) when the determination in the determination step corresponds to the defrosting operation starting condition, and a re-determination step (S160) of determining whether the defrosting operation is finished or not according to defrosting operation finishing condition based on the number of performed heating cycles.

Firstly, in the heating cycle checking step (S100), it is checked whether the air conditioner is in the heating cycle or not.

Here, a case that the air conditioner is firstly operated in a heating mode is defined as a first time heating cycle. In other words, a heating cycle when the air conditioner is operated in the heating mode, performs the defrosting operation once, and is operated in the heating mode is a second time cycle. When, due to this way, the heating cycles are checked, in the defrosting operation of the air conditioner according to the embodiment of the present invention, the defrosting operation starting condition of starting the defrosting operation and a method of performing the defrosting operation is changed according to the number of the heating cycles. This will be described in detail later.

After the heating cycle is checked in the heating cycle checking step (100), whether the defrosting operation starting condition is satisfied is determined according to the number of the heating cycles to determine whether the defrosting operation is started or not (S120).

Although the defrosting operation starting condition is changed according to the number of the heating cycles, the defrosting operation starting condition is determined according to an accumulated driving time t_(a) of the compressor 420 and pipe temperature (not shown) of the outdoor heat-exchanger 430, basically. In other words, the defrosting operation starting condition is satisfied when the accumulated driving time per a cycle of the compressor 420 is greater than a predetermined accumulated driving time t_(a) and the pipe temperature of the outdoor heat-exchanger 430 is equal to or less than a predetermined freezing temperature T_(f).

When the defrosting operation starting condition is satisfied, the first defrosting operating step (S140) of operating the air conditioner in the refrigerating mode to perform the first defrosting operation is carried out.

Here, the first defrosting operation is carried out for the minimal defrosting time t_(m). In other words, in order to guarantee a minimal time required to remove the frost generated on the surfaces of the pipes of the outdoor heat-exchanger 430, the first defrosting operation is compulsorily carried out for the minimal defrosting time t_(m). The minimal defrosting time t_(m) may be determined by experiments. For example, in the present invention, the experiments are carried out by setting the minimal defrosting time t_(m) to six minutes. However, the minimal defrosting time t_(m) is not limited to this, but may have any suitable value.

During the first defrosting operation, the outdoor heat-exchanger serving as an evaporator in the heating operation serves as a condenser to emit heat, and the emitted heat melts the frost covering the surface of the outdoor heat-exchanger.

After performing the first defrosting operation for the minimal defrosting time t_(m), the re-determination step (S160) is carried out for determining whether the defrosting operation finishing condition is satisfied.

The defrosting operation finishing condition is changed according to the number of the heating cycles, but is basically determined according to the pipe temperature (not shown) of the outdoor heat-exchanger 430. In other words, the defrosting operation finishing condition is satisfied when the pipe temperature of the outdoor heat-exchanger 430 is equal to or greater than a predetermined melting point T_(d).

When the defrosting operation finishing condition is satisfied, the defrosting operating step of operating the air conditioner in the refrigerating mode is finished and the air conditioner is operated in the heating mode again to heat the indoor space adequately.

FIG. 4 is a flowchart illustrating a process applied when the number of performed heating cycles checked in the heating cycle checking step (S400) is equal to or less than 5. It is different from the embodiment depicted in FIG. 3 in view of further including a defrosting switching step (S430) after the determination step (S420), and a second defrosting operating step (S470) and a heating switching step (S480) after the re-determination step (S460). The embodiment will be described with reference to the difference.

Firstly, the determination step (S420) determines whether the defrosting operation starting condition is satisfied according to the number of the heating cycles so as to determine whether the defrosting operation is started or not.

Since the defrosting operation starting condition is changed according to the number of the heating cycles, a case that the number of the heating cycles is equal to or less than 2 will be described, and then cases that the number of the heating cycles is equal to or greater than 3 and equal to or less than 5 will be described.

When the number of the heating cycles is equal to or less than 2, the defrosting operation starting condition is when the compressor 420 is operated for the first accumulated driving time t_(a1) and more and the pipe temperature of the outdoor heat-exchanger 430 is equal to or less than a first freezing temperature T_(f1).

In other words, when the air conditioner is operated in the heating mode and the accumulated driving time of the compressor 420 is greater than the first predetermined accumulated driving time t_(a1) and the pipe temperature of the outdoor heat-exchanger 430 is equal to or less than the first predetermined freezing point T_(f1), the defrosting operation starting condition is satisfied.

Here, the first accumulated driving time t_(a1) is a value determined by experiments according to the number of the heating cycles, and uses a value when the outdoor heat-exchanger serves as an evaporator so that frost is generated on the surface of the pipes. For example, in the present invention, 10 minutes is selected as the first accumulated driving time t_(a1). However, the first accumulated driving time is not limited to this value, but any suitable value may be selected.

On the other hand, the first freezing temperature T_(f1) is a value determined by experiments according to the number of the heating cycles, and uses a value when the outdoor heat-exchanger serves as an evaporator so that frost is generated on the surface of the pipes. For example, in the present invention, 14 degrees Fahrenheit is selected as the first freezing temperature T_(f1). However, the first freezing temperature T_(f1) is not limited to this value, but any suitable value may be selected.

When the defrosting operation starting condition is satisfied in the determination step (S420), the defrosting switching step (S430) of operating the air conditioner in the refrigerating cycle is continuously carried out. Here, the defrosting switching step (S430) corresponds to a step of preparing to operate the air conditioner in the refrigerating cycle.

In the defrosting switching step (S430), the compressor 420 and the outdoor blower fan 440 are turned off, the four-way valve 410 is switched from a turning-off state to a turning-on state for a predetermined time period, and the auxiliary heater 220 and the indoor blower fan 240 are turned on when the indoor temperature is equal to or less than a predetermined temperature.

In the defrosting switching step (S430), in order to switch the operating mode of the air conditioner from the heating mode to the refrigerating mode, the compressor 420 is turned off and the outdoor blower fan 440 is stopped. Since an air conditioning system is overloaded by the compressor 420 when the four-way valve 410 is directly turned on, the four-way valve 410 is turned off for a predetermined time period and is switched to the turning-on state. In the present invention, although the four-way valve 410 is under the state of being turned off for about 30 seconds and then is switched to the turning-on state, the time period is not limited to this, but any suitable time period may be selected.

On the other hand, the auxiliary heater 220 and the indoor blower fan 240 are not operated, however when the indoor temperature is equal to or less than a predetermined temperature, the auxiliary heater 220 and the indoor blower fan 240 are operated to heat the indoor space. The predetermined temperature may be selected from one of several values, and in the present invention, the auxiliary heater 220 and the indoor blower fan 240 are operated when the indoor temperature is equal to or less than a desired temperature by 1.5 degrees Fahrenheit.

The defrosting switching step (S430) is continued for a predetermined time period, for example, for 3 minutes in the present invention, but is not limited to this.

After the defrosting switching step (S430), the first defrosting operating step (S440) of operating the air conditioner in the heating mode is started.

In the first defrosting operating step (S440), the compressor 420 and the four-way valve 410 are turned on, and the auxiliary heater 220, the indoor blower fan 240, and the outdoor blower fan 440 are turned off.

Since the air conditioner is substantially operated in the refrigerating mode to perform the defrosting operation in the first defrosting operating step (S440), the compressor 420 is turned on and the four-way valve 410 is turned on so as to switch the circulating cycle of the refrigerant of the air conditioner to the refrigerating mode. By doing so, the high-temperature-and-high-pressure refrigerant of the compressor 420 enters the outdoor heat-exchanger 430 to remove the frost generated on the surfaces of the pipe of the outdoor heat-exchanger 430. On the other hand, when the compressor 420 is operated in the first defrosting operating step (S140), the outdoor blower fan 440 and the auxiliary heater 220 are turned off so as to remove the frost generated on the surfaces of the pipes of the outdoor heat-exchanger 430 more effectively.

Meanwhile, the first defrosting operating step (S440) is carried out for the minimal defrosting time t_(m) as described above. In other words, in order to guarantee a minimal time required to remove the frost generated on the surfaces of the pipes of the outdoor heat-exchanger 430, the first defrosting operation is compulsorily carried out for the minimal defrosting time t_(m).

When the first defrosting operation is carried out for the minimal defrosting time t_(m), whether the defrosting operation finishing condition is satisfied is determined (S460).

The defrosting operation finishing condition when the number of the heating cycles is equal to or less than 2 corresponds to a case when the pipe temperature of the outdoor heat-exchanger 430 is equal to or greater than the first melting point T_(d1). Here, the first melting point T_(d1) is determined by experiments, and a value when the frost is removed from the surfaces of the pipes of the outdoor heat-exchanger 430 is used. For example, in the present invention, the first melting point T_(d1) is selected as 70 degrees Fahrenheit. However, the first melting point T_(d1) is not limited to this, but may be selected as any suitable value.

When the pipe temperature of the outdoor heat-exchanger 430 is equal to or greater than the first melting point T_(d1) in the re-determination step (s460), since the defrosting operation finishing condition is satisfied, a heating switching step (S480) of preparing to operate the air conditioner in the heating mode after the first defrosting operating step (S440) is carried out along a loop B in FIG. 4.

In the heating switching step (S480), the compressor 420 and the outdoor blower fan 440 are turned off, the four-way valve 410 is switched from the turning-on state to the turning-off state for a predetermined time period, and the auxiliary heater 220 and the indoor blower fan 240 are turned on when the indoor temperature is equal to or less than the predetermined temperature.

In the heating switching step (S480), in order to switch the air conditioner from the refrigerating mode to the heating mode, the compressor 420 is turned off and the outdoor blower fan 440 is stopped. Since an air conditioning system is overloaded by the compressor 420 when the four-way valve 410 is directly turned off, the four-way valve 410 is turned on for a predetermined time period and is switched to the turning-off state. In the present invention, although the four-way valve 410 is under the state of being turned on for about 30 seconds and then is switched to the turning-off state, the time period is not limited to this, but any suitable time period may be selected.

On the other hand, the auxiliary heater 220 and the indoor blower fan 240 are not operated, however when the indoor temperature is equal to or less than a predetermined temperature, the auxiliary heater 220 and the indoor blower fan 240 are operated to heat the indoor space. The predetermined temperature may be selected from one of several values, and in the present invention, the auxiliary heater 220 and the indoor blower fan 240 are operated when the indoor temperature is equal to or less than a desired temperature by 1.5 degrees Fahrenheit.

The heating switching step (S480) is continued for a predetermined time period, for example, for 3 minutes in the present invention, but is not limited to this.

When the heating switching step (S480) is finished, one time of the defrosting operation of the defrosting method according to the embodiment of the present invention is finished and the air conditioner is operated in the heating mode to heat the indoor space.

Meanwhile, when the pipe temperature of the outdoor heat-exchanger 430 does not reach the first melting point T_(d1) in the re-determination step (S460), since the defrosting operation finishing condition is not satisfied, the first defrosting operating step (S440) is finished and a second defrosting operating step (S470) and the heating switching step (S480) are carried out sequentially along a loop A in FIG. 4.

Since it is determined that the frost still exists on the surfaces of the pipes of the outdoor heat-exchanger 430 when the pipe temperature of the outdoor heat-exchanger 430 does not reach the first melting point T_(d1) in the re-determination step (S460), the second defrosting operating step (S470) of additionally performing the defrosting operation is carried out.

Meanwhile, in the second defrosting operating step (S470), the air conditioner is operated without exceeding a first additional driving time t_(s1), and the heating switching step (S480) is carried out regardless of the defrosting operation finishing condition when the pipe temperature of the outdoor heat-exchanger 430 does not reach the first melting point T_(d1) for the first additional driving time t_(s1).

In other words, the second defrosting operating step (S470) is carried out for the maximum time period, namely, during the first additional driving time t_(s1), such that the heating switching step (S480) is carried out when the pipe temperature of the outdoor heat-exchanger 430 reaches the first melting point T_(d1). On the other hand, when the pipe temperature of the outdoor heat-exchanger 430 does not reach the first melting point T_(d1) for the first additional driving time t_(s1), the heating switching step (S480) is compulsorily carried out in order to heat the indoor space after the first additional driving time t_(s1). In the present invention, the first additional driving time t_(s1) is selected as 3 minutes, but is not limited and any suitable value may be selected.

Since the heating switching step (S480) thereafter is identical to that described above, the detailed description will be omitted.

Meanwhile, the defrosting operation starting condition when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5 is a case when the compressor 420 is operated above a second accumulated driving time t_(a2) and the pipe temperature of the outdoor heat-exchanger 430 is equal to or less than a second freezing temperature T_(f2). Here, the second accumulated driving time t_(a2) and the second freezing temperature T_(f2) are determined by experiments. In the present invention, like the first accumulated driving time t_(a1) and the first freezing temperature T_(f1), 10 minutes is selected as the second accumulated driving time t_(a2) and 14 degrees Fahrenheit is selected as the second freezing temperature T_(f2), but are not limited to these and may have different values.

In more detail, there are generally two processes of carrying out the defrosting switching step (S430) when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5.

Firstly, when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5, since the defrosting operation starting condition is satisfied when the pipe temperature of the outdoor heat-exchanger 430 is equal to or less than the second freezing temperature t_(a2) at a time when the compressor 420 is operated for the second accumulated driving time t_(a2), the defrosting switching step (S430) is directly carried out.

On the other hand, since the defrosting operation starting condition is not satisfied when the pipe temperature of the outdoor heat-exchanger 430 is greater than the second freezing temperature T_(f2) at a time when the compressor 420 is operated for the second accumulated driving time t_(a2), the pipe temperature of the outdoor heat-exchanger 430 is measured at a predetermined time interval. Due to the measurement, when the pipe temperature of the outdoor heat-exchanger 430 is decreased lower than the second freezing temperature T_(f2), it is determined that the defrosting operation starting condition is satisfied and the defrosting switching step (S430) is carried out after performing the heating operation for an additional heating time t_(w).

Here, when the pipe temperature of the outdoor heat-exchanger 430 at the time of operating the air conditioner for the second accumulated driving time t_(a2) is equal to or greater than the second freezing temperature T_(f2), it is determined that the frost generated on the surfaces of the pipes of the outdoor heat-exchanger 430 is not much and the defrosting switching step (S430) is carried out after the heating operation for the additional heating time t_(w). Meanwhile, in the present invention, the additional heating time is selected as 20 minutes, but is not limited to this and may be selected as any suitable value.

On the other hand, there is a difference between steps after the determination step (S420) when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5 and a case when the number of the heating cycles is equal to or less than 2 in view of the defrosting operation finishing condition and an additional driving time in the second defrosting operating step (S470).

In other words, the defrosting operation finishing condition when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5 is a case when the pipe temperature of the outdoor heat-exchanger 430 is equal to or greater than the second melting point T_(d2). Here, the second melting point T_(d2) is determined by experiments and a value when the frost is removed from the surfaces of the pipes of the outdoor heat-exchanger 430 is used. For example, in the present invention, the second melting point T_(d2) is selected as 70 degrees Fahrenheit. However, the second melting point T_(d2) is not limited to this, but may be selected as a different value.

Moreover, when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5, the second defrosting operating step (S470) is carried out without exceeding a second additional driving time t_(s2). When the pipe temperature of the outdoor heat-exchanger 430 does not reach the second melting point T_(d2) during the second additional driving time t_(s2), the heating switching step (S480) is carried out regardless of the defrosting operation finishing condition. In the present invention, the second additional driving time t_(s2) is selected as 3 minutes like the first additional driving time t_(s1), but is not limited and a different value may be selected.

Since the defrosting switching step (S430), the first defrosting operating step (S440), the re-determination step (S460), the second defrosting operating step (S470), and the heating switching step (S480) except for the defrosting operation finishing condition and the additional driving time of the second defrosting operating step (S470) are identical to the case when the number of the heating cycles is equal to or less than 2, their detailed descriptions will be omitted.

Meanwhile, when the number of the heating cycles is equal to or greater than 6, the process will be carried out according to the flowchart in FIG. 3.

Firstly, a heating cycle checking step (S300) is carried out, and the defrosting operation starting condition is determined when the number of the heating cycles is equal to or greater than 6. (S320).

Here, the defrosting operation starting condition is a case when the compressor is operated over for a third accumulated driving time t_(a3) and the pipe temperature of the outdoor heat-exchanger is equal to or less than a third freezing temperature T_(f3). Here, the third accumulated driving time t_(a3) and the third freezing temperature T_(f3) are determined by experiments. Like the first and second accumulated driving times t_(a1) and t_(a2) and the first and second freezing temperatures, the third accumulated driving time t_(a3) is selected as 10 minutes and the third freezing temperature T_(f3) is selected as 14 degrees Fahrenheit. However, the third driving time and the third freezing temperature are not limited to these, but may have different values.

When the defrosting operation starting condition is satisfied, the first defrosting operating step (S340) is carried out. When the number of the heating cycles is equal to or greater than 6, in the first defrosting operating step (S340), the compressor 420 is turned off, the four-way valve 410 is switched from the turning-off state to the turning-on state for a predetermined time period, the indoor blower fan 240 and the outdoor blower fan 440 are turned on, and the auxiliary heater 220 is turned on when the indoor temperature is equal to or less than the predetermined temperature.

When the number of the heating cycles is equal to or greater than 6, since it is determined that the air conditioner is operated for a long time period, the compressor 420 is turned off, and the four-way valve 410 is under the state of turning-off for a determined time period, for example, for 30 seconds and, after that, is turned off without overload due to a rapid change. On the other hand, the indoor blower fan 240 and the outdoor blower fan 440 are operated to effectively remove the frost on the surfaces of the pipes of the outdoor heat-exchanger 430 during the defrosting operation. The auxiliary heater 220 is not operated, but is driven to heat the indoor space at a preferred temperature when the indoor temperature is decreased under the predetermined temperature. A variety of values may be selected as the predetermined temperature. In the present invention, when the indoor temperature is equal to or less than a desired temperature by 1.5 degrees Fahrenheit, the auxiliary heater 220 is operated, but is not limited to this.

Meanwhile, the first defrosting operating step (S340), as described above, is compulsorily carried out to remove the frost for the minimal defrosting time t_(m).

After carrying out the first defrosting operation for the minimal defrosting time t_(m), the re-determination step (S360) of re-determining the defrosting operation finishing condition is carried out.

The defrosting operation finishing condition when the number of the heating cycles is equal to or greater than 6 is when the pipe temperature of the outdoor heat-exchanger 430 is equal to or greater than a third melting point T_(d3). Here, the third melting point T_(d3) is obtained by experiments. In the present invention, 43 degrees Fahrenheit is selected as the third melting point, but the third melting point is not limited to this and any suitable value may be selected.

In other words, since the defrosting operation finishing condition is satisfied when the number of the heating cycles is equal to or greater than 6 and the pipe temperature of the outdoor heat-exchanger 430 is equal to or greater than the third melting point T_(d3), the first defrosting operating step (S340) is completed.

FIG. 5 is a graph illustrating a time point where the defrosting is started and a time point where the defrosting is finished according to the pipe temperature of the outdoor heat-exchanger. In FIG. 5, an X-axis indicates time and a Y-axis indicates temperature of the surfaces of the pipes of the outdoor heat-exchanger.

Referring to FIG. 5, a time period a represents a heating operation time period, a time period b represents a time period of performing the defrosting switching step (S430), a time period c represents a time period of performing the first and second defrosting operating steps (S440 and S470), a time period d represents a time period of performing the heating switching step (S480), and a time period e represent a time period of performing the heating operating again.

The respective time periods will be described in detail as follows.

Firstly, the air conditioner is operated to heat for the time period a, and the defrosting switching step (S430) is started as described above when the temperature of the surfaces of the pipes of the outdoor heat-exchanger is decreased under the freezing temperature T_(f) (the time period b).

Following the defrosting switching step (S430), the first defrosting operating step (S440) is started for the minimal defrosting time t_(m). Meanwhile, when the temperature of the surfaces of the pipes of the outdoor heat-exchanger does not exceed the melting point T_(d) according to the number of the respective heating cycles, namely, when the defrosting operation finishing condition is not satisfied, the second defrosting operating step (S470) is started. Here, the second defrosting operating step (S470) is not carried out over for the additional driving time t_(s) (the time period c).

When the defrosting operation finishing condition is satisfied during the additional driving time t_(s) of the second defrosting operating step (S470) or when the additional driving time t_(s) is elapsed although the defrosting operation finishing condition is not satisfied, the heating switching step (S480) is carried out (the time period d).

The heating switching step (S480) is a process prepared before starting the heating operation again, and after that, the heating operation is started again (the time period e).

According to the defrosting method of the present invention, the defrosting operation of an air conditioner is changed according to the heating cycle so that the frost generated on the surfaces of the pipes of the outdoor heat-exchanger during the heating operation can be effectively removed.

Moreover, according to the defrosting method of the present invention, the accumulated driving time of a compressor and the freezing temperature of the pipes of the outdoor heat-exchanger, corresponding to the defrosting operation starting condition, are adjusted so that the heating efficiency can be prevented from being deteriorated due to frequent defrosting operations during the heating operation.

Further, according to the defrosting method of the present invention, although the defrosting operation finishing condition is not satisfied during the second defrosting operation, if a predetermined time is elapsed, the defrosting operation is finished so that the time for the defrosting operation can be prevented from being remarkably elongated.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions.

Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. A defrosting method of an air conditioner comprising: an indoor unit including an indoor heat-exchanger, an indoor blower fan, an auxiliary heater; an outdoor unit including an outdoor heat-exchanger, a compressor, an expansion device, and an outdoor blower fan; and a four-way valve to selectively switch a circulation direction of a refrigerant between the indoor unit and the outdoor unit such that the air conditioner is operated in a heating cycle when the four-way valve is turned off and the air conditioner is operated in a refrigerating cycle when the four-way valve is turned on, the defrosting method being selectively determined according to the number of the heating cycles of the air conditioner.
 2. The defrosting method of an air conditioner according to claim 1, comprising: checking the number of the heating cycles of the air conditioner; determining whether a defrosting operation is to be started or not according to a defrosting operation starting condition based on the number of the heating cycles; firstly operating the air conditioner in the refrigerating cycle for a minimal defrosting time when the defrosting operation starting condition is satisfied in the determining; and re-determining whether the defrosting operation is finished or not according to a defrosting operation finishing condition based on the number of the heating cycles.
 3. The defrosting method of an air conditioner according to claim 2, wherein, in the checking, when the number of the heating cycles is equal to or less than 2, the defrosting operation starting condition comprises a case when the compressor is operated over a first accumulated driving time and pipe temperature of the outdoor heat-exchanger is equal to or less than a first freezing temperature.
 4. The defrosting method of an air conditioner according to claim 3, further comprising switching the operation cycle of the air conditioner to the refrigerating cycle when the defrosting operation starting condition is satisfied.
 5. The defrosting method of an air conditioner according to claim 4, wherein, in the switching the operation cycle to the refrigerating cycle, the compressor and the outdoor blower fan are switched to be turned off, the four-way valve is switched from a turning-off state to a turning-on state for a predetermined time period, and the auxiliary heater and the indoor blower fan are turned on when an indoor temperature is equal to or less than a predetermined temperature.
 6. The defrosting method of an air conditioner according to claim 3, wherein, in the firstly operating, the compressor and the four-way valve are turned on, and the auxiliary heater, the indoor blower fan, and the outdoor blower fan are turned off.
 7. The defrosting method of an air conditioner according to claim 3, wherein the defrosting operation finishing condition comprises a case when the pipe temperature of the outdoor heat-exchanger is equal to or greater than a first melting point.
 8. The defrosting method of an air conditioner according to claim 3, further comprising carrying out a heating operation after the firstly operating when the defrosting operation finishing condition is satisfied.
 9. The defrosting method of an air conditioner according to claim 3, further comprising: secondly operating the air conditioner in the refrigerating cycle until the defrosting operation finishing condition is satisfied when the defrosting operation finishing condition is not satisfied; and switching the operation cycle of the air conditioner to the heating operation.
 10. The defrosting method of an air conditioner according to claim 9, wherein the secondly operating is not carried out without exceeding a first additional driving time, and the defrosting method further comprising switching the operation cycle of the air conditioner to the heating operation regardless of the defrosting operation finishing condition when the defrosting operation finishing condition is not satisfied during the first additional driving time.
 11. The defrosting method of an air conditioner according to claim 9, wherein, in the secondly operating, the compressor, the four-way valve, and the outdoor blower fan are tuned on, and the auxiliary heater and the indoor blower fan are turned off.
 12. The defrosting method of an air conditioner according to claim 8, wherein, in the switching the operation cycle to the heating operation, the compressor and the outdoor blower fan are turned off, the four-way valve is switched from the turning-on state to the turning-off state for a predetermined time period, and the auxiliary heater and the indoor blower fan are turned on when the indoor temperature is equal to or less than the predetermined temperature.
 13. The defrosting method of an air conditioner according to claim 2, wherein, in the checking, the defrosting operation starting condition, when the number of the heating cycles is equal to or greater than 3 and equal to or less than 5, comprises a case when the compressor is operated over for a second accumulated driving time and the pipe temperature of the outdoor heat-exchanger is equal to or less than a second freezing temperature.
 14. The defrosting method of an air conditioner according to claim 13, further comprising switching the operation cycle of the air conditioner to the refrigerating cycle when the defrosting operation starting condition is satisfied.
 15. The defrosting method of an air conditioner according to claim 13, further comprising: switching the operation cycle of the air conditioner to the defrosting operation after performing the heating operation for an additional heating time when the pipe temperature of the outdoor heat-exchanger is under the second freezing temperature by measuring the pipe temperature of the outdoor heat-exchanger at a predetermined time interval when the pipe temperature of the outdoor heat-exchanger is equal to or greater than the second freezing temperature after the compressor is operated over for the second accumulated driving time at the defrosting operation starting condition.
 16. The defrosting method of an air conditioner according to claim 14, wherein, in the switching the operation cycle to the defrosting operation, the compressor and the outdoor blower fan are turned off, the four-way valve is switched from the turning-off state to the turning-on state for a predetermined time period, and the auxiliary heater and the indoor blower fan are turned on when the indoor temperature is equal to or less than the predetermined temperature.
 17. The defrosting method of an air conditioner according to claim 13, wherein, in the firstly operating, the compressor and the four-way valve are turned on, and the auxiliary heater, the indoor blower fan, and the outdoor blower fan are turned off.
 18. The defrosting method of an air conditioner according to claim 14, wherein the defrosting operation finishing condition comprises a case when the pipe temperature of the outdoor heat-exchanger is equal to or greater than a second melting point.
 19. The defrosting method of an air conditioner according to claim 13, further comprising switching the operation cycle of the air conditioner from the firstly operating to the heating operation when the defrosting operation finishing condition is satisfied.
 20. The defrosting method of an air conditioner according to claim 13, further comprising: secondly operating the air conditioner in the refrigerating cycle until the defrosting operation finishing condition is satisfied when the defrosting operation finishing condition is not satisfied; and switching the operation cycle of the air conditioner to the heating operation.
 21. The defrosting method of an air conditioner according to claim 20, wherein the secondly operating is not carried out without exceeding a second additional driving time, and the defrosting method further comprising switching the operation cycle of the air conditioner to the heating operation regardless of the defrosting operation finishing condition when the defrosting operation finishing condition is not satisfied during the second additional driving time.
 22. The defrosting method of an air conditioner according to claim 20, wherein, in the secondly operating, the compressor, the four-way valve, and the outdoor blower fan are tuned on, and the auxiliary heater and the indoor blower fan are turned off.
 23. The defrosting method of an air conditioner according to claim 19, wherein, in the switching the operation cycle to the heating operation, the compressor and the outdoor blower fan are turned off, the four-way valve is switched from the turning-on state to the turning-off state for a predetermined time period, and the auxiliary heater and the indoor blower fan are turned on when the indoor temperature is equal to or less than the predetermined temperature.
 24. The defrosting method of an air conditioner according to claim 2, wherein, in the checking, when the number of the heating cycles is equal to or greater than 6, the defrosting operation starting condition comprises a case when the compressor is operated over for a third accumulated driving time and pipe temperature of the outdoor heat-exchanger is equal to or less than a third freezing temperature.
 25. The defrosting method of an air conditioner according to claim 24, wherein, in the firstly operating, the compressor is turned off, the four-way valve is switched from a turning-off state to a turning-on state for a predetermined time period, the indoor blower fan and the outdoor blower fan are turned on, and the auxiliary heater is turned on when an indoor temperature is equal to or less than a predetermined temperature.
 26. The defrosting method of an air conditioner according to claim 24, wherein the defrosting operation finishing condition comprises a case when a pipe temperature of the outdoor heat-exchanger is equal to or greater than a third melting point. 